Daily graph, X-axis in day not in hour?

I’m a new user of Grafana. I want to represent a histogram with daily cumul of duration, but I did not found how to force the X-axis in day and not in day+hour. I want a single bar per day. Here is my data:

> SELECT sum("dheating") FROM "chaudiere" GROUP BY time(24h)
name: chaudiere
time                 sum
----                 ---
2020-02-19T00:00:00Z 0
2020-02-20T00:00:00Z 120
2020-02-21T00:00:00Z 1800
2020-02-22T00:00:00Z 8220

and the parameter of the graph:

Can you please help me?